Regulation of metal utilization ratio and active sites of nickel phyllosilicates for enhanced CO2 methanation

Abstract

This paper proposes a ball milling trio strategy that integrates mechanical exfoliation, liquid-phase exfoliation, and hydrogen peroxide modification to synthesize ultrathin defect-rich Ni-phyllosilicate for CO2 methanation. The obtained catalyst exhibits a unique layered structure with a thickness of only 0.86–1.37 nm and numerous holes, which results in weakened metal-support interaction, enhanced metal utilization ratio, and an appropriate coordination environment for Ni species. Consequently, it displays competitive catalytic activity with a turnover efficiency of CO2 (TOFCO2) of 8.0 × 10–2 s−1 and a low active energy (Ea) of 41.49 KJ·mol−1 for CO2 methanation; importantly, it maintains high stability without Ni sintering and coking in a 100 h-long term test. In-situ diffuse reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS) results confirms the coexistence of *HCOO and *CO intermediates, and density functional theory (DFT) calculations indicate the formate pathway is thermodynamically more feasible, with the rate-determining step of *CO+*OH+*H→*CHO+*OH (ΔE=0.73 eV). Moreover, this method demonstrates high universality in preparing various metal (Fe, Co, Ni, Cu) phyllosilicates and possesses the in-situ regeneration capacity for the deactivated Ni/SiO2 catalyst.